Haven't tried to delay it but have used the MCT/Media Creation Tool to get an .iso file used for creating the bootable DVD [R not RW] disc and creating the bootable USB Thumb drive. What I've seen is Upgrading to Win11 is a 'streaming' install from the Microsoft servers, once started it will remain available until finished regardless of rebooting/restarting the computer.
A side note, I'm having no issues with Win11, most changes are simply in how things are shown and locations of features are different such as the right- of the Start button has more on it than Win10 does, some things from the Control Panel. I got a new Notebook in Oct. '21 [right after Win11 was released] and a new Desktop in Apr. '22 because none of my computers would Upgrade and I needed to know more for the time a client would have an issue. Most things that work in Win10 will work in Win11 and usually a bit faster. The biggest issue is for folks to keep an open mind about the changes, just like we've had to do for a couple 3 decades.